BY FRED SEITZ — The Northwest Branch of the Anacostia and the nearby tributaries in Magruder Park and Hyattsville suffer from the urban insults of runoff, trash, toxic pollutants and excessive sedimentation. Despite these abuses, there is an interesting display of life in both Branch and tributaries, as well as terrestrial and bird residents who depend on this life.
Even a casual stroll through the park and along the Branch bike path provides exposure to the denizens of the not-so-deep watery realms nearby.
The two streams running through Magruder Park flow directly into the Northwest Branch through concrete channels coated with brown algae. This most obvious occupant generally indicates excess runoff, which may include lawn fertilizers and petroleum products that negatively impact the stream. The water around the algae reveals the presence of tiny minnows and a few flies and midges. These “inhabitants” are fairly tolerant of poor water quality.
Early evening walks provide unwelcome visits from the most noxious of the waterborne emergents, mosquitoes. They are very tolerant of poor water quality and are close kin to the flies and midges there. All of these prefer slow-moving, degraded water and some species have a breeding cycle as short as four or days days. While the larvae provide food for some fish, and adult mosquitoes feed many birds and bats in the watershed, they are also responsible for many diseases in animals and humans living nearby.
Other stream inhabitants are the larvae of some of our more attractive local predators, dragonflies and damselflies. They are also relatively tolerant of poor water quality and do us the service of consuming, at the larval stage, many mosquito larvae. When they emerge as adults, they grace the air with their strong flight and colorful appearance and continue to munch on adult mosquitoes and other insects.
The delicate ebony jewelwing damselfly displays its green metallic body and spotted wings as it perches on the jewelweed plants. Its dragonfly cousins, the white tail skimmer and slaty skimmer, are abundant in the morning and afternoon on warm, low wind days. All three are aggressive predators.
Far smaller than the larvae of these dragons and damsels are tiny shrimp-like amphipods, which also inhabit the degraded streams in the swamp. Scuds or side swimmers feed on some of the frogs and salamanders that cohabitate in the wetter areas in Magruder Park. Our local frogs (green frogs, bullfrogs and cricket frogs) are more tolerant of poor water quality than most amphibians, but are also threatened by roadway pollutants and fertilizers. The frogs also consume mosquitoes and flies.
Pulses of polluted or sediment-loaded stormwater can seriously threaten even our more tolerant stream denizens, by introducing more pollutants and washing out stream substrates where the beasties live, feed and lay their eggs. The sedimentation also obscures sunlight needed by the aquatic vegetation that shelters and feeds some of the water dwellers.
Surveys of the Anacostia watershed have consistently shown that the river and its tributaries have been degraded for many years and show far poorer water quality than many other rivers and streams in Maryland.
Part of the degradation of the watershed extends back to colonial times, when tobacco farming silted the harbors. Subsequent development and sprawl have further exacerbated it. While the Anacostia is still a popular spot for boating and fishing, many of the fish taken by anglers also show the scars (or tumors) related to the poor water quality.
While the majority of critters discussed here are small-scale beasties, they represent an important part of the “web of life” in the watery realm, which, of course, impacts terrestrial life. Studying the small water dwellers is not only interesting but it can impress upon us the impact of our own actions and the importance of managing storm water, runoff and other insults to our waterways. Many of the stream insects are important indicators of water quality and should remind us of our connectedness and dependence upon our local waterways, for drinking water, edible fish and recreational uses, such as swimming, fishing and boating. Forgetting these connections and what the small stream monsters tell us can jeopardize our health and enjoyment of our local water world.